The invention relates to an active part for an electric machine, which active part can be configured as a stator or rotor. The active part has slots for arranging coil windings of electric coils. In each case a crosspiece is formed between adjacent slots, and the coil windings can be wound around said crosspiece. A magnetic flux is conducted through the coils by means of the crosspiece.
An active part is understood in conjunction with the invention to be a soft-magnetic component of an electric machine, by means of which component a magnetic flux can be conducted through the coil windings which are arranged in the slots, in order to close a magnetic circuit of the electric machine. The lower a leakage flux of the magnetic circuit, the more efficiently the electric machine can be operated.
Owing to their regular arrangement, the crosspieces are also referred to as stator teeth or rotor teeth. In the electric machines, the stator teeth and rotor teeth are very frequently subjected to a high magnetic flux density, since they perform a flux collecting function of the air gap flux. The induction in these machine parts is consequently higher than in the rest of the machine. However, when there are high flux densities field displacement occurs such as can be explained with the principle of an increase in entropy. This field displacement has the effect that the magnetic field lines are forced from the tooth region into the adjacent slot. Since the magnetic resistance is significantly greater there than in the tooth material, the drop in the magnetic voltage is greater on this path. More magnetomotive force is therefore required, which in turn reduces the efficiency level of the electric machine.
UK 1 114 562 discloses a rotor for a reluctance machine, which rotor does not have any intrinsic magnetic excitement but instead has flux conduction paths between magnetic poles of the rotor. In order to improve the conduction of flux, the rotor is configured in a laminated fashion, resulting in magnetic anisotropy whose preferred direction or easy axis runs in the plane of the lamination layers and whose hard axis runs transversely with respect to the direction of extent of the lamination layers. In contrast to a conventional rotor with a laminated rotor body, the lamination layers therefore do not run perpendicularly with respect to the rotational axis but rather along or parallel to the rotational axis of the rotor.
JP 4343281 B2 discloses a reluctance rotor in which the flux conduction paths are not formed by lamination of the soft-magnetic rotor body but rather by micro-crystalline anisotropy of the iron body.
Document EP 1 696 534 A1 discloses an electric machine in which stator teeth of a stator are fabricated from a magnetically anisotropic material. For this purpose, a magnetic powder can be used as the basic fabrication material. A stator yoke of the stator can also be fabricated from a magnetically anisotropic material. Pole shoes of the stator teeth are fabricated from a magnetically isotropic material.